A capacitor capable of readily supplying electrical energy to an electrical circuit is used in various kinds of power equipment including an inverter (such as a high-voltage inverter), an electric current breaker, a transformer and a high-voltage power source. In addition, in accordance with, among others, differences in internal structure between the capacitors, the voltage ranks of the capacitors, the applications of the capacitors and the types of the power equipment making use of the capacitors, the specifications of the capacitors are completely different from each other.
In a high-voltage inverter for example, normally, inside the inverter (inverter board) or inside an inverter unit composing the inverter, in accordance with the voltage rank, a smoothing capacitor such as an aluminum electrolytic capacitor or a film capacitor is provided. In addition, a snubber capacitor is provided in some cases.
In general, an inverter such as a high-voltage inverter has an insulated gate bipolar transistor (properly referred to hereafter as an IGBT) and a smoothing capacitor electrically connected to the IGBT through a bus bar. In particular, if the inverter is a high-voltage inverter, the smoothing capacitor has a large size so that the capacitor occupies a large space in the inverter. In addition, in order to avoid an insulation failure, it is necessary to provide a spatial distance which is long to a certain degree between bus bars, which are normally provided between the smoothing capacitor and the IGBT, or between a bus bar and a ground frame (that is, a housing composing the inverter).
On top of that, in order to suppress a surge (that is, in order to decrease a suddenly rising voltage), a snubber capacitor is usually provided at a location in close proximity to the IGBT. Since the price of the snubber capacitor is high, however, it is desirable to make the snubber capacitor cheaper (that is, it is desirable to decrease the capacity of the snubber capacitor). In order to solve this problem, there is provided a capacitor described in Patent Document 1 to serve as a capacitor composing a snubber circuit. This capacitor is provided so that a piece of planar resin having a high dielectric constant is in close contact with an area opposite to bus bar.